Evidence of a massive planet candidate orbiting the young active K5V star BD+20 1790

TL;DR

This study presents evidence suggesting a massive planet candidate orbiting the young, active K5V star BD+20 1790, based on radial velocity analysis and stellar activity indicators, marking the youngest star with such a candidate.

Contribution

The paper reports the detection of a potential close-in massive planet around a young star, using combined spectroscopic and photometric data, highlighting the planet's possible role in stellar activity.

Findings

Radial velocity variations indicate a possible planetary companion.

The candidate planet has an orbital period of 7.78 days.

This is the youngest star with a reported planetary candidate.

Abstract

BD+20 1790 is a young active, metal-rich, late-type K5Ve star. We have undertaken a study of stellar activity and kinematics for this star over the past few years. Previous results show a high level of stellar activity, with the presence of prominence-like structures, spots on the surface and strong flare events, despite the moderate rotational velocity of the star. In addition, radial velocity variations with a semi-amplitude of up to 1 km/s were detected. We investigated the nature of these radial velocity variations, in order to determine whether they are due to stellar activity or the reflex motion of the star induced by a companion. We have analysed high-resolution echelle spectra and also two-band photometry was obtained to produce the light curve and determine the photometric period. Based upon the analysis of the bisector velocity span, as well as spectroscopic indices of chromospheric indicators and taking into account the photometric analysis, we report that the best explanation for the RV variation is the presence of a sub-stellar companion. The Keplerian fit of the RV data yields a solution for a close-in massive planet with an orbital period of 7.78 days. The presence of the close-in massive planet could also be an interpretation for the high level of stellar activity detected. Since the RV data are not part of a planet search program, we can consider our results as a serendipitous evidence of a planetary companion. To date, this is the youngest main sequence star for which a planetary candidate has been reported.